No support of .TMX as of yet.
Network support is definitely on the road map (HTTP/GET and HTTP/POST).
With regards to .JSON, Ruby dictionary objects are essentially JSON (just save the file with a .rb extension . Here is an example:
# Dictionary object format one SOME_COOL_DATA = { item_1: 'value 1', item_2: 'value 2' } puts SOME_COOL_DATA[:item_1] # Dictionary object format two SOME_OTHER_COOL_DATA { "item_1" => "value 1", "item_2" => "value 2" } puts SOME_OTHER_COOL_DATA["item_1"]